Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago and resembles a phonograph. That is, the hard drive model includes a storage disk or hard disk that spins at a standard rotational speed. An actuator arm with a suspended slider is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Advances in magnetic recording are also primary reasons for the reduction in size.
However, the decreased track spacing and the overall reduction in HDD component size and weight have resulted in problems with respect to the HGA. Specifically, as the component sizes shrink, a need for tighter aerial density arises. In other words, the HGA is brought physically closer to the magnetic media. In some cases, the HGA will reach “ground zero” or contact recording. However, one of the major problems with contact recording or near contact recording is the effect of vibration on the head portion of the HGA when it encounters the magnetic media or disk. That is, when the slider contacts the disk, dynamic coupling between the slider and the gimbal structure could make the interface unstable and generate a strong or even a sustained slider vibration. The vibration will result in slider flying height modulation thereby degrading read/write performance. This problem is particularly egregious when the drive is a load/unload drive and the gimbal includes a nose limiter extending from the flexure tab under the slider providing an additional moment arm thereby increasing the vibration characteristics.
What is needed is a reliable and repetitive method for damping the vibration due to coupling between the slider and the gimbal structure after disk surface contact. This contact may be generated either during “normal” steady state operation of the hard drive due to the low fly heights or because of loading or unloading events in a load/unload drive, or a shock event during operational state.